The National Highway Traffic Safety Administration proposal announced Friday would apply to passenger vehicles sold after Sept. 1, 2014, and weighing less than 8,500 pounds.

The agency is behind the curve. Automakers have been tucking the devices into cars for years. It automatically records the actions of drivers and the responses of their vehicles in a continuous information loop.

The idea is to gather information that can help investigators determine the cause of accidents and lead to safer vehicles. But privacy advocates say government regulators and automakers are spreading an intrusive technology without first putting in place policies to prevent misuse of the information collected.